The first identification of molluscan Ecsit in the Pacific oyster, Crassostrea gigas, and its expression against bacterial challenge

摘要

The evolutionarily conserved signalling intermediate in Toll pathways (Ecsit) plays crucial roles in innate immunity, embryogenesis and mitochondria-related functions. In this study, the first molluscan Ecsit gene (named as CgEcsit) is isolated from Crassostrea gigas based on the expressed sequence tags-based rapid amplification of cDNA ends polymerase chain reaction (PCR) method. The cloned cDNA of CgEcsit was 1545?bp in length, containing a 1356?bp open reading frame encoding a 451 amino acid protein. Sequence comparison showed that the deduced amino acid sequence of CgEcsit shared approximately 27–33% identities with other known Ecsits from invertebrates and vertebrates. The genomic DNA of CgEcsit covered a length of approximately 6?kb and consisted of six exons and five introns, which represented a closer genomic architecture with Ecsits from vertebrates than that of model invertebrates. The expression pattern of CgEcsit was analysed by real-time quantitative reverse transcript-PCR, in various tissues and especially in haemocytes under vibrio challenge stress. The expression in the haemolymph was challenged dramatically by the bacteria Vibrio anguillarum. These results suggested that Ecsit in C. gigas should be a potential factor of the oyster defence system, and the function and mechanism of CgEcsit might contribute to better disease management strategies of oyster farming.